Leaks from underground storage tanks allow toxic fumes and vapors to escape and collect in areas such as parking garages or basements where they can cause explosions or respiratory illness. Toxic contaminants can also leak into groundwater sources that people depend on for drinking water. Regularly monitoring tanks and pipes minimizes contamination risks.

The tanks contain petroleum products like diesel fuel, gasoline and kerosene. Some even store hazardous substances. The greatest potential hazard is contaminants that seep into the soil and contaminate drinking water supplies.